> On Jun 23, 2020, at 8:19 AM, Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Tue, Jun 23, 2020 at 12:08 AM Song Liu <songliubraving@xxxxxx> wrote:
>>
[...]
>>
>> +BPF_CALL_3(bpf_get_task_stack_trace, struct task_struct *, task,
>> + void *, entries, u32, size)
>> +{
>> + return stack_trace_save_tsk(task, (unsigned long *)entries, size, 0);
>> +}
>> +
>> +static int bpf_get_task_stack_trace_btf_ids[5];
>> +static const struct bpf_func_proto bpf_get_task_stack_trace_proto = {
>> + .func = bpf_get_task_stack_trace,
>> + .gpl_only = true,
>
> why?
Actually, I am not sure when we should use gpl_only = true.
>
>> + .ret_type = RET_INTEGER,
>> + .arg1_type = ARG_PTR_TO_BTF_ID,
>> + .arg2_type = ARG_PTR_TO_MEM,
>> + .arg3_type = ARG_CONST_SIZE_OR_ZERO,
>
> OR_ZERO ? why?
Will fix.
>
>> + .btf_id = bpf_get_task_stack_trace_btf_ids,
>> +};
>> +
>> static const struct bpf_func_proto *
>> raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>> {
>> @@ -1521,6 +1538,10 @@ tracing_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
>> return prog->expected_attach_type == BPF_TRACE_ITER ?
>> &bpf_seq_write_proto :
>> NULL;
>> + case BPF_FUNC_get_task_stack_trace:
>> + return prog->expected_attach_type == BPF_TRACE_ITER ?
>> + &bpf_get_task_stack_trace_proto :
>
> why limit to iter only?
I guess it is also useful for other types. Maybe move to bpf_tracing_func_proto()?
>
>> + *
>> + * int bpf_get_task_stack_trace(struct task_struct *task, void *entries, u32 size)
>> + * Description
>> + * Save a task stack trace into array *entries*. This is a wrapper
>> + * over stack_trace_save_tsk().
>
> size is not documented and looks wrong.
> the verifier checks it in bytes, but it's consumed as number of u32s.
I am not 100% sure, but verifier seems check it correctly. And I think it is consumed
as u64s?
Thanks,
Song
